The present invention relates to compositions for preventing fouling on surfaces exposed to aquatic environments. Several tests relating to antifouling compositions were done with the cooperation and assistance of an international company and dealt with three different tests in which paints were exposed at the company's test station at Kure Beach and later at Harbor Island. There were three tests covering periods of 81/2 months, 401 days, and 2.15 years. The paints tested were composites of Zinc plated on Copper, Copper on Zinc and various other bi-metal alloys. The two of special interest were Copper-Zinc combinations. These flakes were extremely small particles and made excellent paints.
The intermediate series was done several years later by another international company of London, England. Their exposure tests were done in Florida and England and also dealt with the metal composites of special interest, Copper on Zinc and Zinc on Copper. These tests produced results that were contrary to all accepted knowledge. The previous tests were done in a non-leachable vehicle. These were done in a leachable vehicle.
From very early times it was believed that antifouling paints had to be put in a vehicle which permitted poison ions to migrate through the vehicle and their presence at this interface of the paint and electrolyte was what made the paint antifouling. The second company tested both leachable vehicles and non-leachable vehicles. They stated the non-leachable vehicles were unsatisfactory.
A possible explanation is that the antifouling was due to a multiplicity of voltaic cells or emf generators. With this in mind, it was theorized that any combination of dissimilar metals in a suitable vehicle whether leachable or not would create an antifouling paint. What this does is to make possible antifouling paints which do not contain toxic materials such as Copper and its salts (e.g. cuprous oxide) and Mercury and its salts and modern, very expensive, very toxic poisons such as Tributyl Tin Oxide.
No commercial use, so far as is known, has ever occurred as a result of these protracted experiments. There was a reluctance to accept the fact that non-leachable vehicle in hard abrasion resistance vehicle could ever work.
Present antifouling paint compositions are unsatisfactory. When the toxic elements used to prevent fouling are leached out of the paint film they are quickly depleted. These antifouling paints, which are in use use today, are thereby good for only one growing season and must be repainted every year. Also, these leachable paints are badly scratched and damaged by sand when boats are dragged on a beach. This damage will permit fouling to take hold.
The leaching of soluble Copper salts into navigable waters from pleasure crafts, nuclear power plants, and the like is of great concern to State and Federal Authorities especially in the areas of high concentrations of boats, and nuclear power plants. Present antifouling paints are a major cause for such concern.
A world famous authority on antifouling paints explained that tests had been made with superimposed AC current, super-imposed DC current and a combined AC DC current and that all such experiments had been entirely unsuccessful in preventing fouling. He explained that years of experience had shown that all antifouling paints to be effective had to be formulated in a leachable vehicle so that toxic ions could be released into the water in immediate juxtaposition to the antifouling surface and that a non-leachable vehicle had no chance of success.